Telephone call recording may be desirable for several reasons. For example, call recording may enable voice quality analysis to troubleshoot a network. Call recording can also be helpful for training purposes or to maintain an archive for some period of time for subsequent retrieval. Call recording may still also be desired for legal reasons such as lawful intercept. There are two main types of call recording: call data recording and call content recording. Call data recording includes recording call events such as when a call originated, when and by whom a call is terminated, or if a call is forwarded elsewhere. This type of recording may be based on, e.g., what is known as a call detail record (CDR), which captures the phone number of both the person called and the person calling, along with call events and time-date stamps of when the events occurred. In contrast, call content recording involves recording the actual content (e.g., audio) of the call, i.e., the conversation that takes place. Call content recording may also include call data recording.
Many voice calls are now handled by Voice over Internet Protocol (VoIP), which may use, e.g., Session Initiation Protocol (SIP), to set up and tear down sessions over which calls may take place. In a VoIP call, call content is packetized by call endpoints (having unique IP addresses) and transmitted and received over an electronic digital/packet network. In order to record a given call between two endpoints of a VoIP call, “media forking” may be used. Media forking is the process by which the packetized data is copied or cloned at one call endpoint, or at an intermediate location between the endpoints, and the resulting copied or cloned data may then be sent to a recording server or other recording device. In view of the importance of some call recording, it is often desirable to have a backup recording device available in the event a primary call recording device fails.